press on startup to display the bootable disks.
go to disk utility and you have the option to erase there
The fix could be that you are using the wrong startup disk. When you turn your PC or mac on press f1 repeatedly until you come to the startup menu. From this select 'startup' preferences, start up disk and select the right one. If you are unsure there is no harm in trying them all as i doubt you will have more than 2 hard disks.
Restart your computer, then hold the Option (Alt) key as it starts up. Or, use the Startup Disk control panel in Windows or Mac OS X Startup Disk preferences to set the default operating system to use each time the computer starts up.
Built into Mac OS X is an application called Disk Utility, which can format and partition any internal or external volume. It's located in /Applications/Utilities/. Additionally, there are some third-party utilities that can work with partitions on-the-fly: iPartition, DiskWorks, and VolumeWorks all claim to do this.
erase startup-config
In the Applications folder is a folder called Utilities. In the Utilities folder is Disk Utility. Disk Utility will Erase / Partition / Format a hard drive.
Yes you can. Remember if you do this, don't forget to backup your files. Keep your MacBook Air plugged into the charger, and make sure you have an internet connection. Lastly, due your due diligence and research further if you're unsure or unfamiliar about resetting. Once you're ready, go to Apple Menu > Restart. While the Air restarts, hold down the Command and R keys at the same time. Disk Utility should appear, click Continue. You will see a list on the left...select the startup disk, then click Erase. A pop-up menu should appear. Choose Mac OS Extended (journaled). Type a name for your disk, then click Erase. After the disk has erased, choose Disk Utility > Quit Disk Utility. At this point, choose Reinstall Mac OS X and click Continue. Follow the instructions it gives you.
its either a re-writable disk or its not!
The system disk is the partition from which the operating system was loaded at startup.
If your booting from a Mac, when Disk Utility sees the HD, you need to format it as---- Mac OS Extended (Journaled)-----, It will also give you an option of partitioning it into 1 large or many smaller partitions.It WILL ERASE everything on that drive so make sure to select the right one.Disk Utility/select your HD/ Erase/ usually defaults to Mac OS Extended (Journaled) or select it/ name it/ select Erase... to start it.
To select which partition the Mac boots from hold down the Option key (alt) when you start up. In System Preferences select Startup Disk and then select the system you want to set as the default startup.